Method for grafting on polyester fibers with radiation

ABSTRACT

A METHOD OF GRAFT COPOLYMERIZING ACRYLIC ACID OR METHACRYLIC ACID ONTO POLYESTER FIBER BY IRRADIATION WITH IONIZING RADIATION, COMPRISING THE ADDITION OF PYRIDINE, 2-VINYLPYRIDINE, OR 4-VINYLPYRIDINE TO THE REACTION SYSTEM TO INCREASE THE RATE AND THE EFFECTIVENESS OF THE GRAFT COPOLYMERIZATION.

United States Patent 01 ice 3,682,802 Patented Aug. 8, 1972 ABSTRAOT OFTHE DISCLOSURE A method of graft copolymerizing acrylic acid ormethacrylic acid onto polyester fiber by irradiation with ionizingradiation, comprising the addition of pyridine, 2-vinylpyridine, or4-vinylpyridine to the reaction system to increase the rate and theeffectiveness of the graft copolymerization.

SUMMARY OF THE INVENTION This invention relates to a novel method forgraft copolymerizing onto polyester fibers. In particular, the inventionis directed to a novel method for grafting a polymerizable unsaturatedorganic acid onto polyester fibers by irradiation with an ionizingradiation which is characterized by adding pyridine, 2-vinylpyridine, or4- vinylpyridine to said polymerizable unsaturated organic acid, such asacrylic acid or methacrylic acid.

A hydrophobic synthetic fiber, such as polyester or polyolefin fiber,has the drawbacks that the fiber is difiicult to dye, has a poorhygroscopicity and is liable to accumulate electric charge. The methodwhich comprises graft copolymerizing a hydrophilic monomer onto saidfiber is well known as one solution to overcome the mentionedshortcomings. Acrylic acid or methacrylic acid are, for example, broadlyused for that purpose. These are inexpensive monomers which imparthygroscopicity, antistatic property and dyeability, especially for basicdyes, to said fibers. However, since acrylic acid and methacrylic acidhave high rates of polymerization and tend to homopolymerize, their uselowers both the grafting yield, i.e. the fraction of monomer used forthe intended grafting, and the grafting efiiciency. In addition, the useof acrylic acid or methacrylic acid has the further drawback that theresulting homopolymers frequently gel and that their separation from theproduct to be obtained, is difiicult. When said monomers are graftedonto polyester in fiberform, the fibers tend to adhere to each other. Toseparate the fibers, rinsing with a large quantity of a solvent isrequired. However, when the adherence occurs at the same time as thegelling of homopolymers, even rinsing will not be sulficient for theintended separation of the fibers. These factors present thedifiiculties inherent in the process mentioned above.

To overcome these difficulties, a number of studies were made and somesolutions have been suggested. For I for grafting an unsaturated organicacid onto polyester polymer by irradiating said polymer with an ionisingradiation, the improvement which is characterized by adding a retarder,such as a metal or a metal salt, to the reaction system, said retarderpreventing only the homopolymerization of said unsaturated organic acid,and adding further thereto an amount not more than 10%, preferablyODS-3%, on the basis of the volume of said unsaturated organic acid orthe solution thereof, of a benzenoid nuclear substitution compoundhaving the general formula wherein X, Y or Z represent a substituentselected from the group of hydrogen, alkyl, halogen, amino, amido,nitro, ester, phenyl and the substituted radicals thereof, respectively,the number of said substituents being not more than three. However,these methods do not always have satisfactory results.

Therefore, it is an object of this invention to provide a method forreadily grafting acrylic acid or methacrylic acid onto polyester fiberwithout affecting the behavior and the properties of the fiber.

Another object of this invention is to provide a method for increasingthe reaction rate .of the graft copolymerization.

Yet another object is to provide a method of graft c0- polymerizationfor preventing the homopolymerization of acrylic acid and methacrylicacid without any addition of a retarder for said homopolymerization andobtaining a grafted polyester fiber in a desirable state withoutoccurrence of any adherence between the fibers.

Still another object is to provide a method of graft copolymerizationwhereby the reactant fiber is not deteriorated. Other objects of thisinvention will be apparent from the description hereinafter.

The above-mentioned objects of this invention are accomplished by amethod which comprises irradiating a polyester fiber with an ionizingradiation and contacting the fiber with acrylic acid, methacrylic acid,or a solution thereof, whereby pyridine, 2-vinylpyridi1i or4-vinylpyridine is previously added to the reaction system.

In the case of graft copolymerizing acrylic acid or methacrylic acidonto a polyester fiber by the pro-irradiation method or the simultaneousirradiation method with an ionizing radiation, it was found that whefpyridine, 2- vinylpyridine, or 4-vinylpyridine is previously added toacrylic acid or methacrylic acid, the graft copolymerization proceedsmore rapidly than in the case without addition of pyridine or itsderivatives. The homopolymerization of said monomer is prevented withoutany addition of a particular retarder for said homopolymerization, andthe grafted polyester fiber is obtained in a desirable state without thefibers clinging to each other. According to this method, the graftcopolymerization proceeds in the reaction system having a higher pHvalue of 3.0-4.3 than 2.2-2.5 in the case without pyridine and, thedeterioration of the fiber in the course of copolymerization can beprevented. Moreover, especially when the graft copolymerization proceedswith addition of 4-vinylpyridine, it was found that the resulting fiberhaswa' fairly good dyeability for acid dyes, as contrasted with thestarting fiber which has no dyeability or the resulting fiber from thegrafting in the presence of acrylic acidalone or methacrylic acid.

The application of the method of this invention is not limited topolyester in the form of fibers. It can be polyester in the form ofvarious articles, such as filament, tow, sliver, yarn, woven and knittedfabrics and nonwoven aqueous solution of acrylic acid or methacrylicacid, in which 2-vinylpyridine or 4-vinylpyridine has been suspended bymeans of agitation etc. However, it is preferred that an emulsion beformed by adding 0.l-1.0%

fabrics. 5 by volume of a suitable nonionic surfactant (e.g. poly- Inpracticing the present invention, any well-known oxyethylene-sorbitanmonolaurate, sorbitan monolaurate, ionizing radiation effective forgraft copolymerization, or the like) or a cationic surfactant (e.g.stearyltrimethyli.e. corpuscular rays as well as electromagnetic waves,ammonium chloride, cetylpyridinium chloride, or the such as neutrons,X-rays, or at, p, or o-y-rays, may be like). used. Electron beams and-o-rays are especially suitable. The grafted polyester fiber having agrafting yield of The pre-irradiation method as well as the simultaneousmore than 23% obtained according to the method of irradiation method isoperable with these rays. And, the this invention can be dyed with abasic dye, such as exposure dose to be required depends on the desiredgraftcrystal violet, in the same degree as cotton fiber; in coming yieldand the conditions of the grafting reaction beparison, the startingpolyester fiber has no dyeability by cause the grafting yield is ruledby the exposure dose. this color. The grafted polyester fiber hastheadvantage Suitable exposure doses exist bet-ween 10 and 1t) rontof beingdyed to a deep color with a dispersed dye, eig. gens in the case ofpre-irradiation, and between 10 Kayalon Fast Brown, whereas the startingfiber is only and 10 rtintgens in the case of simultaneous irradiation.dyed to medium color. Besides, in the case of 4-vinyl- In the method ofthis invention, the operable amount of pyridine being added to thereaction mixture for the pyridine, 2-vinylpyridine, or 4-vinylpyridineto be added graft copolymerization, it has been found that the graftedto the copolymerizing system is in the range of 5-50 Polyester fiberObtained can he y With an acid y parts to 100 parts of acrylic acid ormethacrylic acid g- Brilliant Scarlet 3R, to a light Shade, Whereas thepartspbeing b l P f bl 1() 3() parts of i. starting fiber is scarcelycolored at all. It can also be dine or 5-20 parts of 2- or4-vinylpyridine on said basis Observed that the hygfoseopleity 0f theresulting fiber is are added. As to the medium, a solution with anorganic enhanced Ovel: that of the startihg fihersolvent, such asmethanol or ethanol, an aqueous disper- The follow g examples areintended to ilhistl'ete the sion, or an emulsion admixed with a suitablesurfactant inventloh, but y Should not be interpreted as limiting may beused. Particularly, when used for copolymerizaits Scopetion the resultwill be very satisfactory with an emulsion EXAMPLE 1 where theconcentration of acrylic acid or methacrylic acid is between 2 and 10%,the concentration of the After p y y terephthalate fiber denier urfatant i maintained below 1%, d 5 50% f ihad been washed with cold waterfor 24 hours and dried, dine, 2-vinylpyridine or 4-vinylpyridine areadded, cal- 100 of the fiber Were Charged into a test tube havingculated on the volume of said monomer. The amount of an Outer diameter0f 1 6111; to this Were added, 5 0f the by-product homopolymer isextremely low and the One of the aqueous acrylic acid solutions havingthe comobtained fibers scarcely adhere to each other. Thus, PositionShown i Table 1 (Containing 05% of P ythis product has an advantage inthat the removal oxyethyieneesolbltah m0Ii0ia11f9-te)- The test tu Wasof homopolymer by rinsing can be omitted, Th h d deaired and sealed off.Then the tube was heated to 50 C. of this application can be effectivelyapplied both to methand irradiated With the 'Y' y ffem Cobalt 60 (doserate acrylic acid, and to acrylic acid. 40 of 1.1X10 riintgens/hour) atthe exposure dose of In the simultaneous irradiation technique, themethod r g n Thereafter, the fiber Was removed r m of this invention canbe equally applied in the presence the test tube, rinsed with water,dried, and weighed. The or absence of air. However, the removal of airor the reresulting weight gain percent is regarded herein as theplacement by nitrogen has the advantage of decreasing grafting yield.The appearance of the fiber between irradithe exposure dose to obtainthe same grafting yield. The ating and rinsing, the amount of thehomopolymer operable temperature at which the irradiation proceedsformed, and the grafting yield are shown in Table 1.

TABLE 1 Composition of Parts of copolymerizing system 1 pyridine (volumeratio) per 100 parts of Grafting Acrylic acrylic yield, Amount ofhomopolymer acid Pyridine Water acid percent formed Adherence 10 0 90 00 Fairly viscous liquid. Scarcely adhering.

9 1 90 12. 2 6. 8 051; m1 No adhering. 8 2 90 25.0 4.8 do No adherence.7 a 90 42.8 2.0 do Do. 6 4 90 66.7 0 -do Do.

1 0.5% of polyoxyethylenesorbitan monolaurate was added to the reactionmixture. In all following examples the same concentration of the sameemulsifier was used.

2 The amount of homopolymer lay-product was estimated from theappearance of the reaction mixture after the irradiation and theprecipitate obtained by pouring the mixture into benzene.

is between 10 and 100 C., preferably between 40 and C. In thepre-irradiation technique, the presence or absence of air during thegraft copolymerization has no relation to the effect of this invention.However, the exposure dose or the period of time for the polymerizationcan be diminished to obtain the same grafting yield, when thepro-irradiation was operated in the absence of air, which may either beremoved or replaced by nitrogen. In that case, the temperature at whichthe polymerization proceeds is preferably between 40 and 100 C.

When the reaction mixture is to be used as an aqueous EXAMPLE 2 Example1 was repeated except that the exposure dose dispersion, the graftcopolymerization can proceed in an was 6.6 10 rontgens. The results areshown in Table 2.

TABLE 2 Composition of Parts of copolymerizing system pyridine (volumeratio) per 100 parts of Grafting Acrylic acrylic yield, Amount ofhomopolymer acid Pyridine Water acid percent formed Adherence 10 90 06.7 Viscous liquid Adhering.

9 1 90 12. 2 11.6 Almost niL... No adhering. 8 2 90 25.0 11.2 do Noadherence. 7 3 90 42.8 5.3 do Do. 6 4 90 66.7 2.0 do Do.

EXAMPLE 3 emulsifier were used in place of the above-mentioned The samestarting polyethylene terephthalate fiber as in Example 1 was used. Bymeans of simultaneous irradiation, the fiber was irradiated at theexposure dose of 15 6.6)(10 rontgens in the pressure of air of the air.Other operating conditions for the graft copolymerization were the sameas in Example 1. The results of the runs are shown in Table 3.

mixture containing pyridine mentioned above. In the latter run, a largequantity of homopolymer was formed and the resulting mixture wasextremely viscous. When removed from the mixture the fibers adhered toeach other to a considerable extent. The homopolymer adhering to thefiber could be removed only by rinsing with hot water. The graftingyield was 3.4%.

TABLE 3 Composition of Parts of copolymerizing system pyridine (volumeratio) per 100 parts of Grafting Acrylic acrylic yield, Amount ofhomopolymer acid Pyridine Water acid percent formed Adherence 1O 0 900 1. 9 Fairly viscous liquid Adherence.

9 1 90 12. 2 7. 6 Almost nil No adherence. 8 2 90 25. 0 5. Do. 7 3 9042. 8 Do.

EXAMPLE 4 EXAMPLE 6 Example 3 was repeated except that the exposure dosewas 2.6)(10 riintgens. The results are shown in Table 4.

After about 100 mg. of the same polyethylene terephthalate fiber as inExample 1 had been charged into TABLE 4 Composition of Parts ofcopolymerizing system pyridine (volume ratio) per 100 parts of GraftingAcrylic acrylic yield, Amount of homopolymer acid Pyridine Water acidpercent formed Adherence 0 90 0 6.6 Large, gelat'lon Extremely adhering.

9 1 90 12. 2 19. 5 Somewhat viscous liquid-.. Somewhat adherence. 8 2 9025. 0 14. 4 scarcely formed No adherence.

7 3 90 42.8 6.6 do No adhering.

EXAMPLE 5 a test tube having the outer diameter of 1 cm., 5 cc. of

After about 100 mg. of the same polyethylene terephthalate fiber as inExample 1 had been irradiated in air with 'y-rays from cobalt 6O (doserate of 13x10 rontgens/hour) at the exposure of 1.0)(10 rontgens, thefiber was charged into a test tube having an outer diameter of 1 cm. 5cc. of a mixture which is composed of acrylic acid, pyridine and waterin the ratio of 9:1:90 and which contains 0.5% of an emulsifier wasadded to the test tube. The whole system was heated at 50 C. for

one of methacrylic acid aqueous solutions of the compositions shown inTable 5 (containing 0.5% of an emulsifier) were added thereto. The testtube was deaired and sealed off. Then the tube was irradiated with'y-rays from cobalt (dose rate of 1.1)(10 rtintgens/hour) at theexposure dose of 2.2 X 10 rontgens. After the reaction, the resultingfiber was removed from the tube. The fiber was rinsed with ethanol,dried and weighed. The weight percent gain is regarded as the graftingyield. The results of the runs 24 hours. After heating, it was foundthat the amount of 55 are shown in Table 5.

TABLE 5 Composition of copolymerizing system Parts of (volume ratio)pyridine per 100 parts of Grafting acrylic methacrylic yield, Amount ofhomopolymer acid Pyridine Water acid percent formed Adherence 10 0 9O 03. 6 Large, blocky gel Remarkably adhering.

9 1 90 12. 2 17. 7 Large, gelation, precipita- Adhering.

mu. 8 2 90 25.0 16. 2 Medium Scarcely adhering. 7 3 90 42. 8 7. 3 Do. 64 90 66. 7 2. 0 Do.

homopolymer formed was small and there was scarcely any adherence amongfibers. The grafting yield of 7.9% was formed after rinsing with coldwater and drying. This result is in contrast to the result from thefollowing run.

Another run was made with the same procedure as in the run mentionedabove except that 5 cc. of an aqueous EXAMPLE 7 Example 1 was repeatedexcept that pyridine in Example 1 was replaced by 2-vinylpyridine. Theresults of graft copolymerizing acrylic acid into polyester fiber aresolution containing 10%. of acrylic acid and 0.5% of an shown in Table6.

TABLE 6 Parts of 2-vinylpyridine Amount of per 100 parts GraftingZ-vinylpyridine of acrylic acid yield Amount of homopolymer formed andused 1 (cc.) (percent) (percent) the appearance of liquid phaseAdherence of fiber 1. 7 Small, Viscous liquid Scarcely adhering. 4. 0Almost I111, clear solution. No adherence. 20 2. do Do. 40 do--. Do. 60.-d0. Do. 80 .do- Do. 100 do..- Do

l The amount 0! 2 -vinylpyridine used per 10 cc. of 10% aqueous acrylicacid solution (containing 0.5% of polyoxyethylenesorbitan monolaurate onthe basis of the reaction mixture).

EXAMPLE 8 EXAMPLE 11 Example 7 was repeated except that the exposuredose was 6.6 10 riintgcns instead of 2.2 10 rontgens. The After about100 of the Same Polyethylene results of the graft copolymerization areshown in Table 7. ephthalate fiber as in Example 1 had been charged intoa TABLE 7 Parts of 2-vinylpyridine Amount of per 100 parts Grafting2-vinylpyrldine of acrylic acid yield Amount of homopolymer formed andused (00.) (percent) (percent) the appearance of liquid phase Adherenceof fiber 0 0 6.7 Large, fairly viscous liquid Adherence. 0.1 10 13.2Almost nil, clear solution No adherence.- 0.2 8.2 .do Do. 0.4-.- 40 4. 7D0. 0.6--. 60 2. 5 D0. 0.8--. 80 3.1 Do. 1 0 100 2. 9 D0.

EXAMPLE 9 test tube having the outer diameter of 1 cm. 5 cc. of any oneof aqueous methacrylic acid solutions of the composition shown in Table10 were added thereto. The air in the test tube was replaced withnitrogen by passing The same polyethylene terephthalate fiber as inExample 7 was used. Example 7 was repeated except that 4-vinylpyridiuewas used instead of 2-vinylpyridine. The

results of graft copolymerization are shown in Table 8. the same for 2minutes, and then the tube was sealed TABLE 8 Parts of 4vinylpyridineper Amount of 4- 100 arts of Grafting vinyl yridlne aory cacid yieldAmount of homopolymer formed used cc.) (percent) (percent) and theappearance of liquid phase Adherence of fiber 0 1.7 Small, viscousliquid Adherence. 10 15.9 Almost nil, clear solution. No adherence. 2010 0 6 D0. D0. 60 Do. 80 Do. 100 Do.

EXAMPLE 10 off. The tube was irradiated with 'y-rays from cobalt 6O(dose rate of 1.1 1O rontgens/hour) at the exposure Example 9 wasrepeated except that the exposure dose dose of 2.2)(10 rontgens. Afterthe reactlon, the resulting was 6.6 10 rontgens instead of 2.2)(10rontgens. The

results of graftmg acryhc and are shown m Table 9. fiber was removedfrom the test tube, rinsed wlth ethanol,

TABLE 9 Parts of 4-vinyl pyridine per Amount of 4- 100 arts of Graftingvinyl yridine acry c acid yield Amount of homopolymer formed used fee.)(percent) (percent) and the appearance of llqllld phase Adherence offiber 0 6. 7 Large, fairly viscous liquid Remarkably adhering. 10 23. 5Almost nil, clear s0lut1on Adherence. 20 193.0 do D0. 40 14.7 0.- Noadherence. 7.6 do. Do. 3.5 0- Do. 1.4 D0.

dried and Weighed. The thus treated fiber had the proper- 75 ties shownin Table 10.

TABLE 10 Parts of 2- vinyl pyridine per 100 parts Amount of 2-vinyl ofmethacrylic pyridine used 1 acid Grafting yiel d Amount of homopolymerformed and l The amount of 2-vlny1pyridine used per 10 cc. of 10%aqueous methacrylic acid solution (containing 0.5% ofpolyoxyethylenesorbitan monolaurate on the basis of the reactionmixture).

As can be seen from Table 10, when 20-40 parts of EXAMPLE 152-vinylpyridine per 100 parts of methacrylic acid were used, theformation of hy-product homopolymer was very Small and the grafted fiberWas Obtained Without mutual fiber as in Example 1 was irridated in theair at the room adherence- When 10 Parts of 2-Vi11y1pyridi11e Were i ittemperature with the electron beam of 1.5 m.e.v., 100 ,uA. Was cer thatthe fate of graft copolymerlzatioh from a Van de Graaff accelerator atthe absorbed dose of remarkably increased though a slight adherence was6.0 Mrad. Thereafter, said fiber was charged into a test caused. tubehaving the outer diameter of 1 cm., and 5 cc. of one EXAMPLE 12 of theaqueous methacrylic acid solutions having the com- Example 11 wasrepeated except that the exposure dose PosltiOhS Shown in Table 14(Containing 0.5% of P ywas 6.6 1O rtintgens instead of 2.2 10 rontgens.The oxyethylenesorbitan monolaurate as emulsifier) e results of graftcopolymerization are shown in Table 11. added thereto. The air in thetest tube was replaced with About 100 mg. of the same polyethyleneterephthalate TABLE 11 Parts of 2-viny1- Amount of pyridine per 2-vinyl100 parts of Grafting pyridine methacrylic yield Amount of homopolymerformed and used (cc.) acid (percent) (percent) the appearance of liquidphase Adherence of fiber 0 6.3 Large, blocky gel Remarkably adhering. 1021. 2 Large, formed as white precipitate...- Adhering. 20 21.4 .-..do Noadherence. 9. 3 Small, formed as white precipita Do. 60 4. 2 Small, paleyellow solution. Do. 80 2. 8 Almost nil, yellow solution. Do. 100 2.3 0Do.

EXAMPLE is nitrogen by passing the same for 2 minutes, and then theample 1 was used. Example 11 was repeated except that tube was sealedoff. Thereafter, the tube was heated at 4-vinylpyridine was used insteadof 2-viny1pyridin The 5 0 C. for 3.5 hours. Table 14 represents thestates of results of graft copolymerization are shown in Table 12.llquld Phase after copolymerilatioh, the eXteIlt 0f mO- The samepolyethylene terephthalate fiber as in Ex- TABLE 12 Parts of 4-vinylpyridine Amount 01'4- per 100 parts Grafting vinyl yridineofmethacrylic yield Amount of homopolymer formed and used 32c.) acid(percent) (percent) the appearance of hquid phase Adherence of fiber 03. 8 Large, clear gel Adherence. 10 24.7 Large, formed as white precipItate.-.. Do. 20 22. 8 Small, formed as white prec1p1tate- Scarcelyadhering. 40 13. 9 Small, clear solution No adherence. 7. 9 Scarcelyformed, clear solution. o. 3. 9 Ahnost nil, clear solution D0. 1. 8...--do Do.

EXAMPLE 14 60 polymer formation, and the grafting yield calculated fromthe increase in weight of the fiber after extracting and removingmethacrylic acid homopolymer.

Example 12 was repeated except that the exposure dose was 6.6 10rtintgens instead of 2.2x 10 riintgens. The results of graftcopolymerization are shown in Table 13.

TABLE 13 Parts of 4- vinylpymdine Amount of 4- per 100 parts Graftingvinyl yridine oimethacrylic eld Amount of homopolyrper formed and usedthe.) acid (percent) (percent) the appearance of liquid phase Adherenceof fiber 0 7.4 Large, clear gel.... Remarkably adhering. 10 34. 2 Large,formed as w Adhering. 20 52. 2 do D0. 40 24. 2 Medium, formed as whiteprecipitate scarcely adhering. 60 21. 6 Scarcely tromed, formed as whiteNo adherence.

precipitate. 80 13. 7 Almost nil, clear solution Do. 100 6.2 ..---do Do.

TABLE 14 Parts of 2-vinyl- Amount of pyridine per 2-vinyl 100 parts ofGrafting pyridine methacrylic yield Amount of homopolymer formed andused (00.) acid (percent) (percent) the appearance of liquid phaseAdherence of fiber 3. 6 Small, clear viscous solution Adherence. 10 19.3 Almost nil, clear solution No adherence; 20 d Do. 40 Do. 60 Do.

Although the present invention has been described with respect tospecific details of certain embodiments thereof, it is not intended thatsuch details serve as limitations of the scope and spirit of the presentinvention.

What is claimed is:

1. In a method for graft copolymerizing polyethylene terephthalatefibers with an organic base and an unsaturated polymerizable organicacid, wherein the fibers are contacted with said organic base and saidorganic acid, the improvement which comprises that the organic base isselected from the group consisting of pyridine, 2-vinylpyridine and4-vinylpyridine, and said organic acid is selected from the groupconsisting of acrylic acid and methacrylic acid, and the resultingsystem is irradiated with ionizing radiation at an exposure dose ofabout 10 -10 rad., the-volume ratio of organic base to polymerizableunsaturated organic acid being between about :95 and 40:60.

2. The improvement of claim 1 wherein the ionizing radiation is selectedfrom the group consisting of gamma rays and electron beams.

3. The improvement of claim 1 wherein said polymerizable unsaturatedorganic acid is in the form of an aqueous emulsion containing about 2 to10% of said acid.

4. The improvement of claim 1 wherein said polymerizable unsaturatedorganic acid is in the form of an aqueous solution containing about 2 to10% of said acid.

5. The improvement of claim 1 wherein the irradiation is carried out atabout 40v"100v C.

6. In a method for graft copolymerizing polyethylene terephthalatefibers, wherein said fibers are pro-irradiated with ionizing radiationat an exposure dose of about IO IO' rad. and the resultingpro-irradiated fibers are contacted with a mixture of an organic baseand a polym- Y erizable unsaturated organic acid, the improvement whichcomprises that said organic base is selected from the group consistingof pyridine, 2-vinylpyridine and 4-vinylpyridine and said organic acidis selected from the group consisting of acrylic acid and methacrylicacid, the volume ratio of organic base to polymerizable unsaturatedorganic acid being between about 5 and 40:60.

7. The improvement of claim 6 wherein said polymerizable unsaturatedorganic acid is in the form of an aqueous emulsion containing about 2 to10% of said acid.

8. The improvement of claim 6 wherein said polymerizable unsaturatedorganic acid is in the form of an aqueous solution containing about 2 to10% of said acid.

9. The improvement of claim 6 wherein the mixture of pre-irradiatedfiber, organic base, and unsaturated organic acid is heated to about40100 C.

References Cited UNITED STATES PATENTS 9/1966 Stanton et a1. 260-8735/1963 Cline et a1. 204159.17

U.S. Cl. X.R. 260-873

